Biomarkers of aging and survival kinetics.
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Aging↗
Biomedical subjects
G Rossolini
Publications and source records attributed to G Rossolini.
Age-related alterations of isoproterenol-stimulated adenylyl-cyclase activity are partially corrected by thymic graft.
Previous experimental results have demonstrated progressive impairments in beta-adrenergic responsiveness with advancing age. Beta-adrenoceptors are involved in the alterations as their density progressively decreases during aging. Alterations in both in vivo responsiveness and receptor density are corrected by neonatal thymic grafts. In the present paper adenylyl-cyclase (AC) activity has been studied in the same animal models used before. Results show that no statistically significant changes can be observed when AC is assayed in absence of beta-adrenergic stimulation. On the contrary, when assayed after Isoproterenol stimulation, AC activity shows a shift of the peak and a decrease of its height in aged animals. A neonatal thymus grafted into old recipients one month before the experiment was performed, is capable of correcting the altered height of the peak but not the peak concentration.
Adenylyl Cyclases↗
Modelling survivorship kinetics: a two-parameter model.
A mathematical model of survivorship kinetics is presented. It takes into account both deterministic and stochastic aspects of survival curves. Earlier reports [Piantanelli: Arch Gerontol Geriatr 1986;5:107-118; Piantanelli: Ann NY Acad Sci 1988; 521:99-109] described a model capable of making distinct predictions on the mean and standard deviation of an index of physiological function, fitting data even in the tail of survivorship curves, and accounting for the selection of the cohort at advanced ages. However, it contains four parameters whose biological interpretation is unclear. In the present paper we propose a modification of the model which maintains the main characteristics of the previous one and, in addition, results in two significant improvements. First, the number of free parameters is reduced to only two, making much easier both their estimation and interpretation, particularly when the model is applied to data from various animal groups manipulated in different ways. Second, it is possible to relate the parameters to well-defined deterministic and stochastic factors: specifically, a deterministic component describing the environmental and genetic influence on physiological functions, and a stochastic component representing the fluctuating interactions of the living organism and its environment.
Aging↗
Role of triiodothyronine in down-regulation and recovery of lymphocyte beta-adrenoceptors in thyroidectomized patients.
Thyroid function modulates beta-adrenergic sensitivity through the regulation of beta-adrenoceptor density. In particular, thyroidectomy decreases and thyroid hormone injections increase beta-adrenoceptor density on human lymphocytes. In the present paper the relationship between receptor modifications and thyroid hormone levels has been studied in human lymphocytes from patients after thyroidectomy. The patterns of early changes as well as recovery trends have been investigated. Results show a statistically significant fall in receptor density, parallelled by a decrease in T3 levels, 1-3 days after thyroidectomy. Recovery of receptor density is observed 5-8 days after surgical intervention and is accompanied by increased T3 levels. There is a positive correlation between receptor density and T3 levels. On the contrary, no statistically significant correlation was observed for receptor density and T4 levels. The time course of disappearance and recovery of receptor density and that of T3 levels have also been analyzed with the aid of a mathematical model fitting experimental data. On this basis, the hypothesis that both down-regulation and subsequent recovery of beta-adrenoceptor density are driven by the fall and rise of T3 is suggested. Data are also discussed in relation to experimental results we have obtained in animal studies.
Adult↗
Thymus-induced recovery of age-related decrease of brain cortex alpha- and beta-adrenoceptors.
It has previously been demonstrated that thymus exerts a regulatory influence on beta-adrenergic system during aging. In particular, it has been shown that thymus can correct the beta-adrenoceptor density decrease in old mice. In the present paper results of experiments are reported dealing with the influence of the thymus on alpha-adrenoceptors of mouse brain cortex. Both subtypes of alpha-adrenoceptors are studied separately, using different labelled ligands. Results show that alpha 1-adrenoceptor density decreases in old animals, while alpha 2-adrenoceptor density does not change significantly. A neonatal thymus grafted into old recipients is capable of correcting the alteration observed in old mice. The differential impairment of alpha-adrenoceptors resembles that one previously observed on beta-adrenoceptors, where beta 1-type decreases in number during aging with a parallel decrease of adenylyl-cyclase activity, while beta 2-type remains unchanged.
Adenylyl Cyclases↗
Thymic involution and aging processes.
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Aging↗